Contact structure having a compliant bump and a test pad

ABSTRACT

A contact structure including a contact pad, a polymer bump and a conductive layer is provided in the present invention. The contact pad is disposed on a substrate. The polymer bump is disposed on the contact pad. The conductive layer covers the polymer bump and extends to the outside of the polymer bump. The portion of the conductive layer extending to the outside of the polymer bump serves as a test pad. The invention further discloses a manufacturing method of a contact structure. First, a substrate is provided having a contact pad already formed thereon. Then, a polymer bump is formed on the contact pad and a conductive layer is formed on the polymer bump. The conductive layer covers the polymer bump and extends to the outside of the polymer bump. The portion of the conductive layer extending to the outside of the polymer bump serves as a test pad.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part application of patent application Ser.No. 11/603,909 filed on Nov. 24, 2006 which claims the priority benefitof Taiwan patent application serial no. 95127901, filed Jul. 28, 2006.This application also claims the priority benefit of Taiwan applicationsserial no. 95139501 and 96101568, filed on Oct. 26, 2006 and Jan. 16,2007, respectively. The entirety of each of the above-mentioned patentapplications is hereby incorporated by reference herein and made a partof this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a contact structure and a manufacturingmethod thereof, especially to a contact structure having a compliantbump and a test pad and a manufacturing method thereof.

2. Description of Related Art

In the field of forming the integrated circuits (IC) of high density,chips need physical structures and electrical structures that are highlyreliable. In order to manufacture within a micro area IC structures ofhigh density, such as liquid crystal panels of high resolution, thecontrol IC used for driving also needs to be closely arranged. Hence,the metal bump on the wafer is used as the conductive contact to servethe purpose.

The U.S. Pat. No. 5,707,902 discloses a bump structure mainlyconstituted by three film layers (metal layer-polymer layer-metallayer). Since the bump structure includes two metal layers, the depththereof is so thick that it is difficult to control the evenness ofetching. As a result, bump structures with fine line distances cannot besuccessfully made.

Further, the bump structure disclosed in the U.S. Pat. No. 5,508,228 hasa top surface narrower than its bottom surface. After the metal layer isformed on the bump structure, a probe is used to contact the metal layeron the bump structure so as to proceed with an electrical test. However,given that the top surface of the bump structure is narrower than thebottom surface thereof, when the electrical test is performed, the probeusually slides off causing the electrical test to fail.

SUMMARY OF THE INVENTION

The present invention provides a contact structure having a compliantbump and a test pad located on the outside the compliant bump to solvethe conventional problem of a sliding probe during an electrical test.

The invention provides a method of manufacturing a contact structure.The contact structure manufactured by the method has a compliant bumpand a test pad located on the outside of the compliant bump.

The invention provides a contact structure including a contact pad, acompliant bump and a conductive layer. The contact pad is disposed on asubstrate. The polymer bump is disposed on the contact pad. Theconductive layer covers the polymer bump and extends to the outside ofthe polymer bump. The portion of the polymer bump covered by theconductive layer forms the so-called compliant bump. The portion of theconductive layer extending to the outside of the polymer bump serves asa test pad.

The invention further discloses a manufacturing method of a contactstructure. First, a substrate is provided and a contact pad has alreadybeen formed thereon. Afterwards, a polymer bump is formed on the contactpad. Then, a conductive layer is formed on the polymer bump. Theconductive layer covers the polymer bump and extends to the outside ofthe polymer bump. The portion of the conductive layer extending to theoutside of the polymer bump serves as a test pad.

In the invention, the conductive layer covering the polymer bump extendsto the outside of the polymer bump and the portion of the conductivelayer extending to the outside of the polymer bump serves as a test pad.Therefore, when a probe is used to conduct an electrical test, the probecan perform the test on the test pad of a large area so that the probecan be prevented from sliding off.

In order to make the aforementioned and other objects, features andadvantages of the present invention more comprehensible, preferredembodiments accompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a contact structureand the steps of an electrical test thereof according to one embodimentof the present invention.

FIGS. 2-6 are schematic cross-sectional views showing contact structuresand the steps of electrical tests thereof according to other embodimentsof the invention.

FIGS. 7A-7F are schematic views showing shapes of the polymer bumps inthe embodiments of the invention.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is a schematic cross-sectional view showing a contact structureand the steps of an electrical test thereof according to one embodimentof the present invention. Referring to FIG. 1, in a manufacturing methodof the contact structure, a substrate 100 is first provided and acontact pad 102 has already been formed thereon. The substrate 100 maybe a silicon substrate, a glass substrate, a printed circuit board, aflexible circuit board or a ceramic substrate. Many electronic elementsor integrated circuits (ICs) may have already been formed in thesubstrate 100. The material of the contact pad 102 may be metal. Themethod of forming the contact pad 102 may be depositing a metal layer onthe substrate 100. Afterwards, the metal layer is patterned by aphotolithography process and an etching process to form the contact pad102. In one preferred embodiment, after the contact pad 102 is formed, aprotective layer 104 is further formed on the substrate 100 and exposesthe contact pad 102. The material of the protective layer 104 may besilicon nitride or other suitable dielectric materials.

Then, a polymer bump 106 is formed on the contact pad 102. The materialof the polymer bump 106 may be polyimide (PI), epoxy, or acrylic. If thematerial of the polymer bump 106 is photosensitive, the polymer bump 106can be formed by a photolithography process. If the material of thepolymer bump 106 is non-photosensitive, the polymer bump 106 can beformed by a photolithography process and an etching process. The polymerbump 106 in a horizontal cross-sectional view may be rectangular (asshown in FIG. 7A), circular (as shown in FIG. 7B), polygonal (as shownin FIG. 7C), cross-shaped (as shown in FIG. 7D), double-cross-shaped (asshown in FIG. 7E), U-shaped (as shown in FIG. 7F) or in other shapes.The invention does not limit the shape of the polymer bump 106.

Afterwards, a conductive layer 108 is formed on the polymer bump 106.The conductive layer 108 covers the polymer bump 106 and extends to theoutside of the polymer bump 106. The portion of the conductive layer 108extending to the outside of the polymer bump 106 serves as a test pad110. The polymer bump 106 and the conductive layer 108 formed thereonconstitute a compliant bump. The conductive layer 108 may extend towardanywhere in the outside of the polymer bump 106, depending on the designof an actual element. In one embodiment of the invention, the materialof the conductive layer 108 may be metal. The conductive layer 108 maycompletely cover the polymer bump 106 (as shown in FIG. 1) or partiallycover the polymer bump 106 (not shown).

Hence, the contact structure formed by the said manufacturing methodincludes a contact pad 102, a polymer bump 106 and a conductive layer108. The contact pad 102 is disposed on a substrate 100. The polymerbump 106 is disposed on the contact pad 102. The conductive layer 108covers the polymer bump 106 and extends to the outside of the polymerbump 106. The portion of the conductive layer 108 extending to theoutside of the polymer bump 106 serves as a test pad 110.

The conductive layer 108 covering the polymer bump 106 extends to theoutside of the polymer bump 106. The portion of the conductive layer 108extending to the outside of the polymer bump 106 serves as a test pad.Thus, when a probe 112 is used to conduct an electrical test, the probe112 can perform the test on the test pad 110 of a large area. Comparedwith the conventional method, where a probe needs to be put on theconductive layer on top of the polymer bump to perform an electricaltest, the present invention has a larger and smooth test pad for thetest to be conducted on so that the probe is prevented from sliding off.

According to another embodiment of the invention, the contact structureof the invention further includes an extending layer 114, as shown inFIG. 2, disposed between the test pad 110 and the substrate 100 (or theprotective layer 104). The material of the extending layer 114 may bethe same as or different from the material of the polymer bump 106. Theextending layer 114 may be formed simultaneously as the polymer bump 106by the same masking process. Furthermore, the height of the extendinglayer 114 is smaller than or equal to the height of the polymer bump106.

In addition, the extending layer 114 and the polymer bump 106 asillustrated in FIG. 2 are separate from each other. Nevertheless, infact, the extending layer 114 and the polymer bump 106 may also beconnected together, as shown in FIG. 3. The main function of theextending layer 114 is protecting the electronic elements or ICs in thesubstrate 100 under the test pad 110 from damage caused by the probe 112when a probe 112 is used to perform an electrical test. If the extendinglayer 114 and the polymer bump 106 are connected together (as shown inFIG. 3), the extending layer 114 may also strengthen the firmness of thepolymer bump 106 and the extending layer 114 so as to prevent thepolymer bump 106 and the extending layer 114 from coming off.

In the embodiments of FIGS. 1-3, the upper surface of the polymer bump106 is a smooth surface, but the present invention is not limited tothese examples. The upper surface of the polymer bump 106 in theinvention may also be a rough surface as shown in FIG. 4. Referring toFIG. 4, the contact structure thereof is similar to that of FIG. 1. Thedifference between them is that the upper surface of the polymer bump106 in FIG. 4 is a rough surface 106 a, and the rough surface 106 a maybe constituted by a plurality of protrusion structures, a plurality ofrecess structures or a plurality of groove-shaped structures. In oneembodiment, the rough surface 106 a is formed simultaneously as thepolymer bump 106 by a method such as a gray level masking process.Moreover, the contact structure shown in FIG. 5 is similar to thecontact structure of FIG. 2. They both include an extending layer 114separate from the polymer bump 106. Their difference is that in thecontact structure of FIG. 5 the upper surface of the polymer bump 106 isa rough surface 106 a. Besides, the upper surface of the extending layer114 may also be a rough surface, and it may be constituted by aplurality of protrusion structures, a plurality of recess structures ora plurality of groove-shaped structures. The contact structure shown inFIG. 6 is similar to the contact structure of FIG. 3. They both includean extending layer 114 connected with the polymer bump 106. Theirdifference is that in the contact structure of FIG. 6 the upper surfaceof the polymer bump 106 is a rough surface 106 a. Similarly, the uppersurface of the extending layer 114 in FIG. 6 may also be a roughsurface, and it may be constituted by a plurality of protrusionstructures, a plurality of recess structures or a plurality ofgroove-shaped structures.

In the foregoing embodiments, whether the contact structure includes anextending layer and whether the upper surface of the polymer bump is arough surface, their common feature is that the conductive layercovering the polymer bump extends to the outside of the polymer bump andthe portion of the conductive layer extending to the outside of thepolymer bump serves as a test pad. Therefore, afterwards, when a probeis used to perform an electrical test, the probe can perform theelectrical test on a test pad of a large area so that the probe can beprevented from sliding off.

Besides, the conductive layer served as the test pad extends from thesurface of the compliant bump towards anywhere in the outside thereof toform a test pad of a large area. Hence, the present invention does notrequire an additional area for the test pad so that the space for theelectronic elements or ICs in the substrate is not occupied or wasted.

If an extending layer is further formed under the test pad, theextending layer can protect the electronic elements or ICs in thesubstrate so as to prevent the electronic elements or ICs from damagecaused when the probe is used to perform the electrical test.

Although the present invention has been disclosed above by theembodiments, they are not intended to limit the present invention.Anybody ordinarily skilled in the art can make some modifications andalterations without departing from the spirit and scope of the presentinvention. Therefore, the protecting range of the present inventionfalls in the appended claims.

1. A contact structure, comprising: a contact pad, disposed on asubstrate; a polymer bump, directly disposed on the contact pad andexposing a portion of the contact pad; and a conductive layer, coveringthe polymer bump and extending to the outside of the polymer bump,wherein the conductive layer contacts the exposed contact pad, and theportion of the conductive layer extending to the outside of the polymerbump serves as a test pad, wherein the test pad is not directly disposedabove the contact pad, and a length of the test pad directly disposedabove the substrate is larger than a width of the polymer bump.
 2. Thecontact structure of claim 1, further comprising an extending layerdisposed between the substrate and the test pad.
 3. The contactstructure of claim 2, wherein the extending layer and the polymer bumpare connected together or separate from each other.
 4. The contactstructure of claim 2, wherein the height of the extending layer issmaller than or equal to the height of the polymer bump.
 5. The contactstructure of claim 2, wherein the material of the extending layer is thesame as or different from the material of the polymer bump.
 6. Thecontact structure of claim 2, wherein the upper surface of at least oneof the extending layer and the polymer bump is a smooth surface or arough surface.
 7. The contact structure of claim 6, wherein the roughsurface is constituted by a plurality of protrusion structures, aplurality of recess structures or a plurality of groove-shapedstructures.
 8. The contact structure of claim 1, further comprising aprotective layer disposed on the substrate and exposing the contact pad.9. The contact structure of claim 1, wherein the material of the polymerbump comprises polyimide (PI), epoxy or acrylic.
 10. The contactstructure of claim 1, wherein the conductive layer completely covers thepolymer bump or partially covers the polymer bump.
 11. The contactstructure of claim 1, wherein the substrate comprises a siliconsubstrate, a glass substrate, a printed circuit board, a flexiblecircuit board or a ceramic substrate.
 12. The contact structure of claim1, wherein the polymer bump in a horizontal cross-sectional view isrectangular, circular, polygonal, cross-shaped, double-cross-shaped orU-shaped.
 13. A contact structure, comprising: a contact pad, disposedon a substrate; a polymer bump, directly disposed on the contact pad andexposing a portion of the contact pad; a conductive layer, covering thepolymer bump and contacting the exposed contact pad; and a test pad,connecting to the conductive layer, wherein the test pad is disposed onthe substrate and does not overlap with the contact pad, and a length ofthe test pad is larger than a width of the polymer bump.